This invention is related to the field of polyolefins. Particularly, this invention relates to the field of phosphite additives to polyolefins.
Polymers are used in a variety of diverse applications. For example, such applications include food packaging, electronic components, automobile parts, fibers and fabrics, and medical equipment. Polymers could not perform such diverse functions without the assistance of a very broad range of polymer additives. Without additives, polymers can degrade during processing and over time can lose impact strength, discolor, and become statically charged. Additives not only overcome these and other limitations, but also can impart improved performance properties to the final product.
One type of additive is antioxidants which usually are used to retard the oxidative degradation of polymers. Degradation can be initiated when free radicals, highly reactive species with an unpaired electron, are created in polymers by heat, ultraviolet radiation, mechanical shear, and/or metallic impurities. It is believed when a free radical is formed, a chain reaction can begin that initiates polymeric oxidation. Subsequent reaction of the radical with an oxygen molecule can yield a peroxy radical, which then can react with an available hydrogen atom to form an unstable hydroperoxide and another free radical. In the absence of an antioxidant, these reactions can become self-propagating and can lead to polymer degradation.
There are two basic types of antioxidants, primary and secondary antioxidants. It is believed that primary antioxidants can intercept and stabilize free radicals by donating active hydrogen atoms. It also is believed that secondary antioxidants can prevent formation of additional free radicals by decomposing unstable hydroperoxides into a stable product. When primary antioxidants, such as hindered phenols, are utilized, polymers can have a more yellow color than unstabilized polymers, therefore decreasing the commercial value of polymers. Secondary antioxidants, such as phosphite compounds, often are utilized to increase the stability and whiteness of polymers.
Unfortunately, phosphite additives also can create difficulties in polymer production and applications. First, some phosphite additives are hygroscopic and upon absorption of water, phosphites can clump and can be difficult to feed into the polymer production process. Some phosphites are hydrolytically unstable and can react with water resulting in a lower active phosphite concentration for stabilizing polymers. Furthermore, this hydrolysis reaction can leave moisture and acidic residues in polymers. There is a need in the polyolefin industry for a hydrolytically stable phosphite additive product that increases polymer stability and improves the whiteness of polymers.
It is an object of this invention to provide a composition comprising a polyolefin that has improved color and stability.
It is another object of this invention to provide a process to produce a composition comprising a polyolefin that has improved color and stability.
It is a further object of this invention to provide a process to improve the hygroscopic nature and hydrolytic stability of phosphites.
It is yet another object of this invention to provide a process to improve the melt strength of recycled polyolefins.
It is yet another object of this invention to provide an article of manufacture prepared from said polyolefin produced by this invention.
In accordance with the present invention, a composition of matter is formed by combining components comprising:
a) a polyolefin;
b) a first phosphite, which is an arylalkyl diphosphite having a formula, 
wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical;
c) a second phosphite selected from the group consisting of:
(i) a second arylalkyl diphosphite of formula (I), wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical, which is different from said first arylalkyl diphosphite and
(ii) a triarylphosphite having a formula, 
wherein R1, R2, R3, R4, and R5 are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical;
d) a hindered phenol; and
e) water.
A second embodiment of this invention provides a process comprising blending:
a) a polyolefin;
b) a first phosphite, which is an arylalkyl diphosphite having a formula, 
wherein R1, R2, R3, R4, R5, R6, R7 , R8 , R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical;
c) a second phosphite selected from the group consisting of:
(i) a second arylalkyl diphosphite of formula (I), wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical, which is different from said first arylalkyl diphosphite and
(ii) a triarylphosphite having a formula, 
wherein R1, R2, R3, R4, and R5 are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical;
d) a hindered phenol; and
e) water.
A third embodiment of this invention provides a process to reduce the hygroscopic nature and to improve the hydrolytic stability of phosphites comprising blending:
a) a first phosphite, which is an arylalkyl diphosphite having a formula, 
wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical and
b) a triarylphosphite having a formula, 
wherein R1, R2, R3, R4, and R5 are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical.
A fourth embodiment of this invention provides a process to improve the stability of recycled polyolefins comprising blending:
a) a polyolefin;
b) a first phosphite, which is an arylalkyl diphosphite having a formula, 
wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical;
c) a second phosphite selected from the group consisting of:
(i) a second arylalkyl diphosphite of formula (I), wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical, which is different from said first arylalkyl diphosphite and
(ii) a triarylphosphite having a formula, 
wherein R1, R2, R3, R4, and R5 are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical.
d) hindered phenol; and
e) water.
A fifth embodiment of this invention provides an article of manufacture prepared from a polymer produced by a process comprising the step of blending:
a) a polyolefin;
b) a first phosphite, which is an arylalkyl diphosphite having a formula, 
wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical;
c) a second phosphite selected from the group consisting of:
(i) a second arylalkyl diphosphite of formula (I), wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical, which is different from said first arylalkyl diphosphite and
(ii) a triarylphosphite having a formula, 
wherein R1, R2, R3, R4, and R5 are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical;
d) a hindered phenol; and
e) water.
The term xe2x80x9cpolyolefinxe2x80x9d, as used in this invention, includes homopolymers as well as copolymers of olefinic compounds. Usually, said homopolymers are comprised of one mono-1-olefin having about 2 to about 10 carbon atoms per molecule, preferably, about 2 to about 6 carbon atoms per molecule. Exemplary mono-1-olefins, which produce polyolefins with excellent properties, include, but are not limited to, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene. Most preferably, said mono-1-olefin is ethylene due to its ease of use in this invention.
Applicable copolymers comprise at least 2 different mono-1-olefins, a monomer and one or more comonomers, each having from about 2 to about 16 carbon atoms per molecule. Preferably said monomers, which produce polyolefins with excellent properties, include, but are not limited to, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene, most preferably, said mono-1-olefin is ethylene, due to ease of use in the present invention. Exemplary comonomers include, but are not limited to, aliphatic 1-olefins, such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, and other higher olefins and conjugated or non-conjugated diolefins such as 1,3-butadiene, isoprene, piperylene, 2,3-dimethyl-1,3-butadiene, 1,4-pentadiene, 1,7-hexadiene, and other such diolefins and mixtures thereof. Preferably, said copolymer is comprised of ethylene and a higher alpha-olefin comonomer having from about 3 to about 16 carbon atoms per molecule. Propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene are especially preferred comonomers for use with ethylene due to ease of copolymerization and best resultant copolymer properties. Usually, said polymers are comprised of about 1 to about 20 weight percent comonomers based on the total weight of the polyolefin.
Generally, a polyolefin can be obtained through polymerization of an olefinic compound or compounds by conventional techniques known in the art. For example, a polyolefin can be produced by solution polymerization, slurry polymerization, or gas phase polymerization using conventional equipment and contacting processes. The term xe2x80x9cneatxe2x80x9d polyolefin, as used in this disclosure, means a polyolefin produced from a process prior to the addition of any additives. Preferably, a polyolefin can be prepared in the presence of an inorganic oxide supported chromium oxide catalyst system, due to its excellent polyolefin production capabilities. As used in this disclosure, the term xe2x80x9csupportxe2x80x9d refers to a carrier for another catalytic component. Any support useful to support catalyst systems can be used. Exemplary inorganic oxide catalyst system supports include, but are not limited to, inorganic oxides, either alone or in combination, phosphated inorganic oxides, and mixtures thereof. Particularly preferred are supports selected from the group consisting of silica, silica-alumina, alumina, fluorided alumina, silated alumina, thoria, aluminophosphate, aluminum phosphate, phosphated silica, phosphated alumina, silica-titania, coprecipitated silica/titania, fluorided/silated alumina, and mixtures thereof Most preferably, the inorganic oxide of an inorganic oxide supported chromium oxide catalyst system is a silica-titania support.
As a result of polymerization by a chromium oxide catalyst system supported on a silica-titania support, a polyolefin can contain a minor amount of titania in the recovered polyolefin. Such polyolefins can contain from about 1 mg/kg to about 10 mg/kg, based on the mass of neat polyolefin, titanium catalyst residue calculated as titanium. It is believed that catalyst residue comprising titanium can contribute to increasing discoloration of polyolefins upon addition of hindered phenols.
Chemical additives frequently are combined with polymers to improve selected physical properties of polymers. For example, antioxidants can be added to improve heat, light, and oxidation stability. As defined in this disclosure, the xe2x80x9cstabilityxe2x80x9d of a polymer is an indication or measure of how the polymer is affected by external forces, such as, for example, light, heat, and oxygen, acting on or reacting with the polymer. Stability, in other words, is a measure of changes that can occur in and/or to the polymer.
Hindered phenols are often utilized as a primary antioxidant, however, hindered phenols can discolor polyolefins. Phosphite additives can be utilized to remedy this discoloration problem providing whiteness to polyolefins, and in addition, phosphite additives also can improve the stability of polyolefins. However, some phosphite additives are hygroscopic, and upon absorption of water, phosphites can clump and can be difficult to feed into polymer production processes. Some phosphites are hydrolytically unstable and can react with water, thereby resulting in a lower active phosphite concentration for stabilizing polymers. Furthermore, this hydrolysis reaction can leave moisture and acidic residues in polymers.
Surprisingly, it has been discovered in this invention, that the addition of two specific phosphites to polyolefins can produce a polyolefin having improved color and stability over polyolefins containing only one of the two phosphites. The composition comprises a polyolefin, a first phosphite, which is an arylalkyl diphosphite having a formula, 
wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical, and a second phosphite selected from the group consisting of:
(i) a second arylalkyl diphosphite of formula (I), wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical, which is different from said first arylalkyl diphosphite and
(ii) a triarylphosphite having a formula, 
wherein R1, R2, R3, R4, and R5 are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical.
Preferably, R2, R4, R5, R7, R9 , and R10 in said first phosphite are hydrogen and R1, R3, R6, and R8 are mixed aliphatic and aromatic organic radicals having from about 1 to about 20 carbon atoms per radical. As used in this disclosure, xe2x80x9cmixed aliphatic and aromatic organic radicalsxe2x80x9d are radicals with both an aliphatic component and an aromatic component. Most preferably, said first phosphite is bis(2,4-dicumylphenyl)pentaerythritol disphosphite since it provides the best resultant polymer color and stability. Bis(2,4-dicumylphenyl) pentaerythritol disphosphite can be obtained commercially from Dover Chemical Corporation under the name Doverphos(copyright)S-9228. Depending on the synthesis methods and conditions employed, bis(2,4-dicumylphenyl)pentaerythritol diphosphite can contain up to about 15% of the cage formation as disclosed in U.S. Pat. No. 5,428,086, hereinafter incorporated by reference.
Preferably, R2, R4, R5, R7, R9, and R10 in said second arylalkyl diphosphite are hydrogen and R1, R3, R6, and R8 are selected from the group consisting of straight-chained and branched organic radicals having from about 1 to about 20 carbon atoms per radical. Most preferably, said second arylalkyl diphosphite is bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite since it provides the best resultant polymer stability and color. Bis(2,4-di-tertbutyl) pentaerythritol disphosphite can be obtained commercially from GE Specialty Chemicals under the names Ultranox(copyright) 626, which is in powder form, Ultranox(copyright)626A, which is in free flowing granular form, and Ultranox(copyright) 627A, which is in free flowing form and contains an inorganic neutralizer.
Preferably, R2, R4, and R5 in said triarylphosphite are hydrogen and R1 and R3 are selected from the group consisting of straight-chained and branched organic radicals having from about 1 to about 20 carbon atoms per radical. Said straight-chained and branched organic radicals include, but are not limited to, methyl, tert-butyl, and 1,1-dimethylpropyl. Exemplary triarylphosphites include, but are not limited to, tris-(2,4-di-tert-butylphenyl phosphite; tris-(2-tert-butylphenyl) phosphite; tris-[2-(1,1-dimethylpropyl)-phenyl] phosphite; and tris-[2,4-di-(1,1-dimethylpropyl)-phenyl] phosphite. Most preferably, said triarylphosphite is tris(2,4-di-tert-butylphenyl) phosphite since it can provide improved resultant polymer stability and color. Tris(2,4-di-tert-butylphenyl) phosphite can be obtained commercially from Dover Chemical Corporation under the name Doverphos(copyright) S-480.
Said first phosphite and second phosphite can be present in a total phosphite amount within a range of about 100 mg/kg to about 20,000 mg/kg based on the mass of neat polyolefin. Concentrations below 100 mg/kg can be insufficient to improve color and improve stability of said polyolefins, and amounts above 20,000 mg/kg may exceed U.S. Food and Drug Administration limitations, increase costs, and provide no additional benefit to said polyolefins.
Preferably, said first phosphite and second phosphite are present in a total phosphite amount within a range of about 100 mg/kg to about 2000 mg/kg based on the mass of the neat polyolefin, most preferably, within a range of 100 mg/kg to 900 mg/kg based on the mass of neat polyolefin. These preferred ranges are optimum since they provide the best polyolefin color and stability at minimum cost.
Generally, said second phosphite can be present in the polymer in an amount within a range of about 2% to about 90% by weight of the total amount of said first and second phosphite added to said neat polyolefin. Concentrations below about 2% by weight based on the total amount of phosphites added can be insufficient to improve color and improve stability of said polyolefins, and amounts above about 90% by weight based on the total amount of phosphites added fail to provide the synergistic effects of improved polyolefin color and stability caused by said first phosphite. Preferably, said second phosphite is present in the polymer in an amount within a range of about 5% to about 75% by weight of the total amount of said first and second phosphite added to said neat polyolefin, most preferably, said second phosphite is present in the polymer in an amount within the range of 10% to 50% of the total amount of said first and second phosphite added to said neat polyolefin. These preferred ranges have been shown to provide the best synergistic effects between said first and said second phosphite to improve polyolefin color and stability.
There are many different hindered phenols which are equally suitable for use in the invention either singly or in combination with each other that are well known to those skilled in the art. The hindered phenol is selected from the group consisting of monophenols, bisphenols, thiobisphenols, polyphenols, hydroxybenzyl aromates, amides of xcex2-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid, esters of xcex2-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid with mono- or polyvalent alcohols, Spiro compounds, and mixtures thereof.
Exemplary monophenols include, but are not limited to, 2,6-di-tert-butyl-4-methylphenol; 2-tert-butyl-4-methoxyphenol; and 4-(hydroxymethyl)-2,6-di-tert-butylphenol.
Exemplary bisphenols include, but are not limited to, 2,2xe2x80x2-methylene-bis-(6-tert-butyl-4-methylphenol); 2,2xe2x80x2-methylene-bis-(6-tert-butyl-4-ethylphenol); 2,2-methylene-bis-[4-methyl-6-(xcex1-methylcyclohexyl)-phenol]; 1,1-bis-(5-tert-butyl-4-hydroxy-2-methyl-phenyl)-butane; 2,2-bis-(5-tert-butyl-4-hydroxy-2-methylphenyl)-butane; 2,2-bis-(3,5-di-tert-butyl-4-hydroxyphenyl)-propane; 1,1,3-tris-(5-tert-butyl-4-hydroxy-2-methylphenyl)-butane; 2,2-bis-(5-tert-butyl-4-hydroxy-2-methylphenyl)-4-n-dodecylmercapto-butane; 1,1,5,5,-tetra-(5-tert-butyl-4-hydroxy-2-methyl-phenyl)-pentane; ethylene glycol-bis-[3,3-bis-(3xe2x80x2-tert-butyl-4xe2x80x2-hydroxyphenyl)-butyrate]; 1,1-bis-(3,5-dimethyl-2-hydroxyphenyl)-3-(n-dodecylthio)-butane; and 4,4xe2x80x2-thio-bis-(6-tert-butyl-3-methylphenol).
Exemplary thiobisphenols include, but are not limited to, 4,4xe2x80x2-thiobis(6-tert-butyl-m-cresol); 1,1 xe2x80x2-thiobis(2-naphthol); and 2,2xe2x80x2-thiobis(4-methyl-6-tert-butylphenol).
Exemplary polyphenols include, but are not limited to, tetrakis(methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)methane; 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-benzene; 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate; and tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane.
Exemplary hydroxybenzyl aromates include, but are not limited to, 1,3,5-tri-(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene; 2,2-bis-(3,5-di-tert-butyl-4-hydroxybenzyl)-malonic acid-dioctadecyl ester; 1,3,5-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-isocyanurate; and 3,5-di-tert-butyl-4-hydroxybenzyl-phosponic acid-diethyl ester.
Exemplary amides of xcex2-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid include, but are not limited to, 1,3,5-tris-(3,5-di-tert-butyl-4-hydroxyphenyl-propionyl-hexahydro-s-triazine and N,Nxe2x80x2-di(3,5-di-tert-butyl-4-hydroxyphenyl-propionyl)-hexamethylenediamine.
Exemplary hindered phenols include, but are not limited to, esters of xcex2-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid with mono- or polyvalent alcohols, such as with methanol, octadecanol, 1,6-hexanediol, ethylene glycol, thiodiethylene glycol, neopentyl glycol, pentaerythritol, and tris-hydroxyethyl-isocyanurate.
Exemplary spiro compounds include, but are not limited to, diphenolic spiro-diacetals or spiro-diketals, such as, for example, 2,4,8,10-tetraoxaspiro-[5,5]-undecane substituted in the 3- and 9-position with phenolic radicals, such as 3,9-bis-(3,5-di-tert-butyl-4-hydroxyphenyl)-2,4,8,10-tetraoxaspiro-[5,5]-undecane and 3,9-bis-[ 1,1-dimethyl-2-(3,5-ditert-butyl-4-hydroxyphenyl)-ethyl]-2,4,8,10-tetraoxaspiro-[5,5]-undecane.
Preferably, hindered phenols are selected from the group consisting of tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane; 1,3,5-tri-(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene; xcex2-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid-n-octadecyl ester; 2,6-di-tert-butyl-4-methyl-phenol; 3,9-bis-[1,1-dimethyl-2-(3,5-di-tert-butyl-4-hydroxy-phenyl)-ethyl]-2,4,8,10-tetraoxaspiro-[5,5]-undecane, and mixtures thereof. These preferred hindered phenols provide improved color and stability for polyolefins.
Most preferably, said hindered phenol compound is tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane, since it provides excellent color and stability polyolefin properties. Tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane can be obtained commercially from Ciba-Geigy Corporation as Irganox(copyright) 1010.
Generally, the hindered phenol is present in an amount less than about 5000 mg/kg based on the mass of neat polyolefin. Preferably, said hindered phenol is present in an amount within the range of about 1 mg/kg to about 2000 mg/kg based on the mass of neat polyolefin. Most preferably, said hindered phenol is present in an amount within a range of 50 mg/kg to 1000 mg/kg based on the mass of neat polyolefin. Hindered phenol concentrations above 5000 mg/kg can exceed FDA limits and increase production costs, and phenol concentrations below 50 mg/kg can be too low to ensure polyolefin stability.
In accordance with this invention, it has been found that the addition, or presence, of water can improve the color of said polyolefin over polyolefins without water. Generally, water must be present in an amount within a range of about 1 mg/kg to about 5000 mg/kg based on the mass of neat polyolefin. Preferably, water is present in an amount within a range of about 1 mg/kg to about 2000 mg/kg based on the mass of neat polyolefin. Most preferably, water is present in an amount within a range of 1 mg/kg to 1000 mg/kg based on the mass of neat polyolefin. Water concentrations above 5000 mg/kg can cause bubbles in the polyolefin making it commercially unacceptable, while water concentrations less than 1 mg/kg may not improve the color of said polyolefin.
Water added to said polyolefin can have a pH within a range of about 4 to about 10. Preferably, said water can have a pH within a range of about 6 to about 8. A pH lower than 4 can cause production equipment to corrode, and water at a pH higher than 10 can react with the hindered phenol reducing the stability of the polyolefin.
The resulting stabilized polyolefin compositions of this invention comprised of said polyolefin, said first and second phosphite, said hindered phenol, and water may optionally also contain various conventional additives, such as the following:
(1) Antioxidants, including, but not limited to,
(1.1) Alkylated hydroquinones, such as, for example, 2,6-di-t-butyl-4-methoxyphenol; 2,5-di-t-butyl-hydroquinone; 2,5-di-6-amyl-hydroquinone; and 2,6-diphenyl-4-octadecyloxyphenol;
(1.2) Hydroxylated thiodiphenyl ethers, such as, for example, 2,2xe2x80x2-thio-bis-(6-t-butyl-4-methylphenol); 2,2xe2x80x2-thio-bis-(4-octylphenol); 4,4xe2x80x2-thio-bis-(6-t-butyl-3-methylphenol); and 4,4xe2x80x2-thio-bis-(6-t-butyl-2-methylphenol);
(1.3) Benzyl compounds, such as, for example, 1,3,5-tris-(3,5-di-t-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene; bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfide; isooctyl-3,5-di-t-butyl-4-hydroxybenzyl-mercapto-acetate; bis-(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)dithiolterephthalate; 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate; 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate; dioctadecyl-3,5-di-t-butyl-4-hydroxybenzyl-phosphonate; calcium salt of monoethyl 3,5-di-t-butyl-4-hydroxybenzylphosphonate; and 1,3,5-tris-1,3,5-dicyclohexyl-4-hydroxybenzyl)isocyanurate;
(1.4) Acylaminophenols, such as, for example, 4-hydroxy-lauric acid anilide; 4-hydroxy-stearic acid anilide; 2,4-bis-octylmercapto-6-(3,5-t-butyl-4-hydroxy-anilino)-s-triazine; and octyl-n-(3,5-di-t-butyl-4-hydroxyphenyl)-carbamate;
(1.5) Esters of xcex2-(5-t-butyl-4-hydroxy-3-methyl-phenyl)-propionic acid with monohydric or polyhydric alcohols, such as, for example, methanol; diethyleneglycol; octadecanol; triethyleneglycol; 1,6-hexanediol; pentaerythritol; neopentylglycol; tris-hydroxyethyl isocyanurate; thiodiethyleneglycol; N,Nxe2x80x2-bis(hydroxyethyl)oxalic acid diamide; and di-hydroxyethyl oxalic acid diamide;
(2) UV absorbers and light stabilizers
(2.1) 2-(2xe2x80x2-Hydroxyphenyl)-benzotriazoles, such as, for example, the 5xe2x80x2-methyl-, 3xe2x80x2,5xe2x80x2-di-t-butyl-, 5xe2x80x2-t-butyl-, 5xe2x80x2-(1,1,3,3-tetramethylbutyl)-, 5-chloro-3xe2x80x2-, 5xe2x80x2-di-t-butyl-, 5-chloro-3xe2x80x2-t-butyl-5xe2x80x2-methyl-, 3xe2x80x2-sec-butyl-5xe2x80x2-t-butyl, 4xe2x80x2-octoxy, 3,5xe2x80x2-di-t-amyl-, and 3,5xe2x80x2-bis-(xcex1,xcex1-dimethylbenzyl)-derivatives;
(2.2) 2-Hydroxy-benzophenones, such as, for example, the 4-hydroxy-, 4-methoxy-, -octoxy-, 4-decyloxy-, 4-dodecyloxy-, 4-benzyloxy-, 4,2xe2x80x2,4xe2x80x2-trihydroxy-, and 2xe2x80x2-hydroxy-4,4xe2x80x2-dimethoxy-derivatives.
(2.3) Esters of substituted and unsubstituted benzoic acids, such as, for example, phenyl salicylate; 4-t-butyl-phenyl-salicylate; octylphenyl salicylate; dibenzoyl-resorcinol; bis-(4-t-butylbenzoyl)-resorcinol; benzoylresorcinol; 2,4-di-t-butyl-phenyl-3,5-di-t-butyl-4-hydroxybenzoate; and hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate;
(2.4) Acrylates, such as, for example, xcex1-cyano-xcex2,xcex2-diphenylacrylic acid ethyl ester or isooctyl ester; xcex1-carbomethoxy-cinnamic acid methyl ester; xcex1-cyano-xcex2-methyl-p-methoxy-cinnamic acid methyl ester or butyl ester; xcex1-carbomethoxy-p-methoxy-cinnamic acid methyl ester; and N-(xcex2-carbomethoxy-xcex2-cyano-vinyl)-2-methyl-indoline.
(2.5) Nickel compounds, such as, for example, nickel complexes of 2,2xe2x80x2-thio-bis-[4-(1,1,3,3-tetramethylbutyl)-phenol], such as the 1:1 or 1:2 complex, optionally with additional ligands such as n-butylamine, triethyanolamine or N-cyclohexyl-di-ethanolamine, nickel dibutyl-dithiocarbamate, nickel salts of 4-hydroxy-3,5-di-t-butylbenzylphosphonic acid monoalkyl esters, such as of the methyl, ethyl or butyl ester, nickel complexes of ketoximes such as of 2-hydroxy-4-methyl-pentyl undecyl ketoxime, and nickel complexes of 1-phenyl-4-lauroyl-5-hydroxy-pyrazol, optionally with additional ligands.
(2.6) Sterically hindered amines, such as, for example bis-(2,2,6,6-tetramethylpiperidyl)-sebacate; bis-(1,2,2,6,6-pentamethylpiperidyl)-sebacate; n-butyl-3,5-di-t-butyl-4-hydroxybenzyl malonic acid; bis-(1,2,2,6,6-pentamethylpiperidyl)ester; condensation product of 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidine and succinic acid; condensation product of N,Nxe2x80x2-(2,2,6,6-tetramethylpiperidyl)-hexamethylendiamine and 4-t-octylamino-2,6-dichloro-1,3,5-s-triazine; tris-(2,2,6,6-tetramethylpiperidyl)-nitrilotriacetate; tetrakis-(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,5-butane-tetracarbonic acid; 1,1xe2x80x2-(1,2-ethanediyl)-bis-(3,3,5,5-tetramethylpiperazinone). Such amines include hydroxylamines derived from hindered amines, such as di-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)sebacate; 1-hydroxy-2,2,6,6-tetramethyl-4-benzoxypiperidine; 1-hydroxy-2,2,6,6-tetramethyl-4(3,5-di-t-butyl-4-hydroxyhydrocinnamoyloxy)piperidine; and N-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)-xcex5-caprolactam.
(2.7) Oxalic acid diamides, such as, for example, 4,4xe2x80x2-di-octyloxy-oxanilide; 2,2xe2x80x2-di-octyloxy-5,5-di-t-butyl-oxanilide; 2,2xe2x80x2-di-dodecyloxy-5,5xe2x80x2-di-t-butyl-oxanilide, 2-ethoxy-2xe2x80x2-ethyl-oxanilide; N,Nxe2x80x2-bis(3-dimethylaminopropyl)-oxalamide; 2-ethoxy-5-t-butyl-2xe2x80x2-ethoxyanilide and its mixture with 2-ethoxy-2xe2x80x2-ethyl-5,4xe2x80x2-di-t-butyloxanilide and mixtures of o-methoxy and p-methoxy as well as of o-ethoxy and p-ethoxy disubstituted oxanilides.
(3) Metal deactivators, such as, for example, N,Nxe2x80x2-diphenyloxalic acid diamide; N-salicylal-Nxe2x80x2-salicyloylhydrazine; N,Nxe2x80x2-bis-salicyloylhydrazine; N,Nxe2x80x2-bis-(3,5-di-t-butyl-4-hydroxyphenylpropionyl)-hydrazine; salicyloylamino-1,2,4-triazole; bis-benzylidene-oxalic acid dihydrazide.
(4) Phosphites and phosphonites, such as, for example, triphenyl phosphite; diphenylalkyl phosphites; phenyldialkyl phosphites; tris(nonyl-phenyl) phosphite; trilauryl phosphite; trioctadecyl phosphite; distearyl pentaerythritol diphosphite; tris(2,4-di-t-butyl-phenyl)phosphite; diisodecyl pentaerythritol diphosphite; bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite; tristearyl sorbitol triphosphite; and tetrakis(2,4-di-t-butylphenyl) 4,4xe2x80x2-biphenylene diphosphonite.
(5) Peroxide scavengers, such as, for example, esters of xcex2-thiodipropionic acid, for example, the lauryl, stearyl, myristyl or tridecyl esters, mercaptobenzimidazole or the zinc salt of 2-mercaptobenzimidazole, zinc-dibutyl-dithiocarbamate, dioctadecyldisulfide, pentaerythritol-tetrakis(xcex2-dodecyl-mercapto)-propionate.
(6) Polyamide stabilizers, such as, for example, copper salts in combination with iodides and/or phosphorus compounds and salts of divalent manganese.
(7) Basic co-stabilizers, such as, for example, melamine, polyvinylpyrrolidone, dicyandiamide, triallyl cyanurate, urea derivatives, hydrazine derivatives, amines, polyamides, polyurethanes, alkali metal salts and alkaline earth metal salts of higher fatty acids for example calcium stearate, barium stearate, magnesium stearate, sodium ricinoleate, potassium palmirate, antimony pyrocatecholate and zinc pyrocatecholate.
(8) Nucleating agents, such as, for example, 4-t-butyl-benzoic acid, adipic acid, and dephenylacetic acid.
(9) Fillers and reinforcing agents, such as, for example, calcium carbonate, silicates, glass fibers, asbestos, talc, kaolin, mica, barium sulfate, metal oxides and hydroxides, carbon black, and graphite.
(10) Aminoxy propionate derivatives, such as, for example, methyl-3-[N,N-dibenzylaminoxy]propanoate; ethyl-3-[N,N-dibenzylaminoxy]propanoate; 1,6-hexamethylene-bis[3-(N,N-dibenzylaminoxy)propionate]; methyl-[2-(methyl)-3-(N,N-dibenzylaminoxy)propionate]; octadecyl-3-[N,N-dibenzyl-aminoxy]propanoic acid; tetrakis[N,N-dibenzylaminoxy)ethyl carbonyl oxymethyl]methane; octadecyl-3-[N,N-diethylaminoxy]propanoate; 3-[N,N-dibenzylaminoxypropanoic acid potassium salt; and 1,6-hexamethylene-bis[3-(N-allyl-N-dodecyl aminoxy)propionate].
(11) Other additives, such as, for example, plasticizers, lubricants, emulsifiers, pigments, optical brighteners, flame-proofing agents, antistatic agents, blowing agents and thiosynergists such as dilaurylthiodipropionate or distearylthiodipropionate.
(12) Other additives, such as, for example, oxazaphospholidines, may additionally or alternatively be present.
To produce a polyolefin with improved color, stability, and melt strength after recycling, a process is employed comprising blending the following components:
a) a polyolefin;
b) a first phosphite, which is an arylalkyl diphosphite having a formula, 
wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical;
c) a second phosphite selected from the group consisting of:
(i) a second arylalkyl diphosphite of formula (I), wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms, which is different from said first arylalkyl diphosphite and
(ii) a triarylphosphite having a formula, 
wherein R1, R2, R3, R4, and R5 are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical;
d) a hindered phenol; and
e) water.
The combination of said first phosphite, said second phosphite and water with said polyolefin improves color over polyolefins produced without water or a second phosphite. In addition, polyolefin stability is improved by the use of the combination of said first phosphite and said second phosphite.
Furthermore, when the first phosphite and the second phosphite are added to said polyolefin, recycled polyolefins or reworked polyolefins have improved melt strength through two regrind passes. As defined in this disclosure, xe2x80x9crecycled polyolefinsxe2x80x9d or xe2x80x9creworked polyolefinsxe2x80x9d are polyolefins that have been reground or pelletized after having been previously processed by molding, extrusion or other applications. xe2x80x9cRegrind passesxe2x80x9d is defined as the number of times the polyolefin is ground into pieces to be reused in new applications. Melt strength is a measure of the strength of the plastic while in the molten state.
Any of the additives herein discussed, excluding water, can be combined with said polyolefins according to any method known in the art and at any time after formation of said polyolefin in production processes, or prior to, during, or after fabrication into articles. While phosphite additives are typically incorporated into polyolefins prior to fabrication into articles, it is also possible to apply the phosphite additives by a topical application to the finished articles. Exemplary methods of combining said phosphite additives with said polyolefin, include, but are not limited to, mixing, pelletizing, extruding, and mixtures thereof. The phosphite additives can be preblended together and then combined with said polyolefin, or said phosphite additives can be combined individually with said polyolefin. Said phosphite additives may be in solid form, solution, or a slurry. Said polyolefin can be in any form, such as, for example, fluff, powder, granulate, pellet, solution, slurry, and/or emulsion.
Water can be combined with a polyolefin prior to, during, and/or after fabrication of the polyolefin into articles. Water can be added by any method known in the art including water spray or steam injection systems. Preferably, water at ambient temperature is routed via a pumping system to the throat of an extruder, and most preferably, water is added via an atomization spray system. These methods are preferred since uniform water addition can be obtained.
Another embodiment of this invention is a process to reduce the hygroscopic nature and to improve the hydrolytic stability of phosphites comprising blending:
(i) a first phosphite, which is an arylalkyl diphosphite having a formula, 
wherein R1, R2, R3, R4, R R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical and
(ii) a triarylphosphite having a formula, 
wherein R1, R2, R3, R4, and R5 are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical.
Some triarylphosphite are hydrolytically resistant while said arylalkyl diphosphites can be hydrolytically prone. When said arylalkyl diphosphites and said triarylphosphites are combined, the phosphite blend has a reduced hygroscopic nature and has improved hydrolytic stability.
A further embodiment of this invention is an article of manufacture prepared from a polymer produced by a process comprising blending:
a) a polyolefin;
b) a first phosphite, which is an arylalkyl diphosphite having a formula, 
wherein R1, R2, R3, R4, R5, R6, R7, R8, R9 , and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical;
c) a second phosphite selected from the group consisting of:
(i) a second arylalkyl diphosphite of formula (I), wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 can be the same or different and are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical, which is different from said first arylalkyl diphosphite and
(ii) a triarylphosphite having a formula, 
wherein R1, R2, R3, R4, and R5 are selected from the group consisting of hydrogen and straight-chained or branched, cyclic or acyclic, aromatic or aliphatic, and mixed aliphatic, aromatic, and/or cycloaliphatic organic radicals having from about 1 to about 20 carbon atoms per radical;
d) a hindered phenol; and
e) water.
Said article of manufacture can be produced by any means known in the art, such as, but not limited to, extrusion, blow molding, injection molding, and thermoforming.